318 VEGETABLE SUBSTANCES. 



In order to ascertain the state of fermentation it was 

 recommended to dip a pen, at intervals of every 

 quarter of an hour, into the contents of the vat, and 

 to make with it a few strokes on paper : when the 

 marks thus made are colourless, it is the proper 

 period for arresting the fermentation. Much practical 

 skill is required in seizing on this moment, in which 

 the fermenting mixture assumes the appearance of a 

 liquor, holding in suspension a distinct green pulp, 

 which by slight agitation speedily and completely 

 separates and falls to the bottom, leaving a clear gold- 

 coloured supernatant fluid. The whole of the turbid 

 green liquor is then discharged from the steeping 

 vat, and passes into the second vessel. The first 

 vat is then immediately cleansed, fresh plants are 

 thrown in, and the work proceeds without inter- 

 mission. The refuse matter is carefully removed 

 from the house as soon as taken out. The noxious 

 odour of this refuse occasions the peculiar unhealthi- 

 ness' incident to the occupation. 



As soon as the liquor is received into the second 

 vat, it is violently beaten by the repeated fall of 

 wooden buckets, full of holes, and fixed to long 

 handles moved by manual labour or other power. 

 A more complicated mechanical contrivance is some- 

 times employed. This agitation of the parts, by 

 checking any farther fermentation, prevents putridity, 

 and especially promotes the separation of the grain, 

 as it is technically called, or the dark coloured 

 granular pulp, which is the indigo. The whole of 

 the liquor and of the pulp change during the process 

 from green to deep blue. A large quantity of air- 

 bubbles are also expelled by the beating. Lime- 

 water is most usually added at this time, as it greatly 

 assists in the formation of the grain. When the 

 grain, on being left in a quiescent state for a brief 

 period, separates readily from the liquor which holds 







